Wow, this looks really cool, at least from an effects point of view.

I'm curious as to how the story will get the viewer to care about the characters, since they're not fighting, and the robots are not alive, but let's see what the concept is.

According to the IMDb, this is based on the Twilight Zone episode "Steel." That might answer your question to some extent.

I don't see why there should be a problem, though. Presumably, there will still be human characters building/repairing the robots, promoting the fights, betting on the outcome, etc. There's plenty of opportunity to care about the humans, since their careers are basically dependent on the robots' performance. The robots are kind of their surrogates.

Just saw it. It was very enjoyable. Like a sci-fi version of Rocky. Not sure what the reason was for that ending, but it was a very entertaining popcorn film.

---Nits & Notes
Trailer Nit: In the trailer when Max asks Bailey what Charlie was like as a boxer, Bailey says he was a top contender, ranked Number 2 in the world. In the movie, however, we see that she wasn't describing Charlie, but a guy that Charlie fought and lost to.

Shouldn't there be a secure area, even in underground matches, for the robot operators (Roboperators?) to sit, where unauthorized people cannot sabotage the match, and for that matter, where they can't be endangered by the robots? Why do Charlie and Max stand right where Atom and Metro are fighting in that zoo sandpit, rather than find higher ground?

Is it really helpful to put a bench in the corner for the robot to sit on? I know they're trying to maintain the boxing motif, but this was just funny, and I'm not sure it was intentional. Since robots can remaining standing even when they're turned off, they're obviously not conserving any energy by having him sit the way they'd do with a human boxer, so what good is a bench? Even if Charlie and Max need to work on his circuits, couldn't Atom just kneel? Why complicate things and take up precious time with another unnecessary piece of equipment?

The use of the shadow function was not only a nice sci-fi plot point, but also functioned to underscore how the robots were essentially avatars for the human side of the story, in particular, Charlie's never having won the championship. When they first discover Atom has one, Bailey says they're rare. Why is this? Why has the entire robot boxing community not clued into the usefulness of this feature? Tak Mashido himself says that Zeus has the ability to evolve and rewrite his own boxing codes, so you'd think he of all people would recognize the value of this function. (I guess it's possible that the boxing community simply evolved the way it has due to historical contingencies, and that the idea will probably spread to incorporate expert boxers with the techies, now that Charlie was seen using it in a match.)

---Spoiler Nit (highlight to read)
Why did the creators have Atom lose the final match? It certainly wasn't implausible, but what was the narrative function? Did they want to maintain Atom and Charlie's underdog status? Were they attempting to closely mirror (shadow?) or even give a deliberate shout-out to the end of the first Rocky movie? Or were they just leaving things open for a sequel?

Luigi, the whiteout didn't work. Spoiler's there without highlighting.

Arrgh. Thanks, Scott. I formatted the white dashes to indent the words "Spoiler Nit", and then forgot to do so with the nit itself. Well, at least the red Spoiler Nit note was there, so hopefully people knew to avoid reading it. I've fixed that.

I also added an additional nit that I forgot to include when I first wrote the post.